Field of the Invention
The present invention concerns a process and a device for the manufacture of lined panels, particularly for interiors of motor vehicles and vehicles in general.
Said panels are preferably formed by a supporting element consisting of a plate of thermoplastic material, being thick enough and featured as to provide the panel with adequate mechanical resistance, and by a covering which is often of mixed type, namely constituted by two portions of covering different from each other. Generally said portions respectively consist of calendered plastic, or imitation leather, and of fabric, lying contiguously on the molded plate. However, the mixed covering may be formed by two or more parts of differently colored calendered plastic or by two or more parts of different fabrics.
The reciprocal arrangement of the areas varies according to the panel design required; for instance, in the case of calendered/fabric, the fabric portion may occupy an area of the panel such as to be joined to the area covered with imitation leather by a junction line and/or open superimposition line, or may present one or more areas of fabric thoroughly comprised within the portion of imitation leather covering. In the latter case the junction and/or superimposition line is a line closed on itself. A panel of this type is generally manufactured by using dies formed by two complementary portions reproducing the final shape of the panel. The plate of preheated thermoplastic material and the covering, stretched on a positioning frame above said plate, are placed between the two portions of the die, which, when closing, couples them to each other thus forming the lined and molded panel.
However, the use of coverings of mixed type involves problems of correct positioning between covering and plate. In fact, during molding, the different covering areas, namely for instance the portions of fabric and imitation leather, must be positioned with sufficient precision in correspondence with the relevant areas on the plate they will occupy in the final configuration of the shaped and lined panel. An even higher precision is moreover required in the case where creation of the so-called "shadow effect" is desired, i.e. that particular aesthetic effect which is obtained by positioning the junction and/or superimposition line between the different materials of the covering inside corresponding slots provided on the supporting plate during molding. It is therefore obvious that the positioning of said junction line with respect to the plate must be as more precise as possible to preserve the narrow tolerance limits present in this case.
Said exact positioning is however made difficult by the fact that the covering, which is originally plate-like, is shaped following by the final shaping of the panel, so that the covering tends to displace under the action of the stresses and deformations occurring during the molding stage.
To ensure a correct positioning several types of techniques were used, such as for example the one featuring the use of half-dies wherein pressing members are provided, for instance dandy rolls, which carry the covering portion, in correspondence with the PVC/fabric junction line, in contact with the plate before the panel molding operation.
Said system allows the problem of exact positioning to be effectively solved, but it has also proved to be expensive and complex to be performed, mainly due to the need of producing half-dies provided with said dandy rolls.